Endothelial lipase (EL) is a Triglyceride Lipase family on a par with Lipoprotein Lipase (LPL) and Hepatic Lipase (HL). Studies in the knockout mouse and transgenic mouse have indicated that EL is associated with HDLc metabolism by the strong phospholipase activity, and EL is accepted as a factor which regulates plasma HDLc levels (Non-Patent Document 1).
Plasma HDLc levels have been accepted as an inverse correlate of coronary artery disease (CAD) risk. HDLc is supposed to have an anti-atherosclerotic effect through acceleration of reverse cholesterol transport accompanied with anti-oxidizing and anti-inflammatory effects. Low HDLc levels are accepted as one of the risk factors of CAD.
Therefore, an EL inhibitor serves as a therapeutic agent for CAD through its effect of increasing HDLc levels. Actually, an increase of HDLc levels and a decrease of atherosclerotic lesion area have been reported in EL-deficient atherogenic mice (Non-Patent Document 2).
These facts suggest the possibility of a selective inhibitor of EL as a therapeutic agent for dyslipideamia and atherosclerosis.
Patent Document 1, 2 and 3 disclose various compounds having an inhibitory activity on hepatic lipase and/or endothelial lipase, but oxadiazole derivative such as the present compound has not been disclosed.
Patent Document 4 discloses a compound having inhibitory activity on triglyceride lipase, lipoprotein lipase, hepatic lipase, pancreatic lipase or endothelial lipase, but oxadiazole derivative such as the present compound has not been disclosed.
Patent Document 5 to 15 disclose various compounds having inhibitory activity on EL, but oxadiazole derivative such as the present compound has not been disclosed.
Patent Document 16 discloses an oxadiazole derivative having inhibitory activity on PDF (peptide deformylase). For example, the following compound is disclosed.

But patent document 16 does not describe any inhibitory activity on EL and the increasing activity of HDLc.